With the development in digital technologies for electronic devices in recent years, demands for a non-volatile variable resistance element which has a greater capacity, higher writing and reading speed, and longer-life and which consumes lower power in writing have been increased, for storing data such as images. To meet such demands, efforts in miniaturizing flash memories using existing floating gates are said to have limitations.
A non-volatile variable resistance element using perovskite material (Pr(1-x)CaxMnO3 [PCMO], LaSrMnO3 [LSMO], and GdBaCoxOy [GBCO], for example) has been proposed as a first conventional technique that could possibly meet the demands above (See PTL 1). With this technique, voltage pulses (a short-duration waveform voltage) having different polarities are applied to the perovskite material to increase or decrease the resistance value and the resistance value that changes is associated with data, thereby storing the data.
There also is a non-volatile variable resistance element which utilizes the characteristics of a film of transition metal oxide (NiO, V2O, ZnO, Nb2O5, TiO2, WO3, or CoO), that is, a resistance value changes when voltage pulses having different pulse widths are applied to the film of the transition metal oxide, as a second conventional technique that enables switching resistance values using a homopolarity voltage pulse (See PTL 2). In another implemented configuration of the variable resistance element using a transition metal oxide film, cross-point type memory arrays using a diode are stacked.
[Citation List]
[Patent Literature]
    [PTL 1] U.S. Pat. No. 6,204,139    [PTL 2] Japanese Unexamined Patent Application Publication No. 2004-363604